Speaking as a Moscow court on Friday begins a “Kafkaesque” trial of her dead husband, Natalya Zharikova, 40, in her first ever media interview, urged Britain to adopt a similar law to the Magnitsky Act approved by the United States in December.

The Act, which introduced US visa bans and asset freezes for Russian officials allegedly involved in Mr Magnitsky’s death in a Moscow jail in 2009, prompted fury from the Kremlin, which approved a controversial ban on American parents adopting Russian children as a “symmetrical response”.

Mrs Zharikova and husband

“I would like the UK Government to introduce a similar law to the US Magnitsky Act,” Ms Zharikova told The Daily Telegraph. “Many people in the UK clearly understand the matter and sympathise with us. If it’s not possible to get justice in Russia then it should be found elsewhere.”

Mr Magnitsky died in agony in a pre-trial detention centre aged 37 after being beaten and denied essential medical treatment for pancreatitis. He had been jailed a year earlier by senior Russian police officers whom he accused of organising a £140m fraud in league with tax officials.

No one has been convicted over his death, which provoked outrage worldwide and has become a symbol of corruption and ruthlessness under President Vladimir Putin.

Britain and Russia embarked on a mini-thaw last week, when William Hague, the Foreign Secretary, and Philip Hammond, the Defence Secretary, welcomed their Russian counterparts, Sergei Lavrov and Sergei Shoigu, to London for a rare bilateral meeting. Relations remain fraught however over the poisoning of former KGB officer Alexander Litvinenko in Britain in 2006. Any move to ban Russian officials from entering the UK is likely to incense Moscow.

Mr Hague said before his meeting with Mr Lavrov that foreign human rights violators could be anonymously denied visas to Britain, but there is now growing pressure for the Government to "name and shame" Mr Magnitsky's abusers and publicly block their entry.

Three former Foreign Secretaries – Sir Malcolm Rifkind, David Miliband and Jack Straw - have expressed their support for an explicit entry ban on Mr Magnitsky's alleged tormentors, who include state officials, judges and police. Other backbench MPs are also lobbying for such a measure.

Moscow's Tverskoy Court will today begin a posthumous trial of Magnitsky on fraud charges with an empty defendant's cage in the room, guarded by bailiffs. The lawyer is accused of an £11m tax avoidance scam in what his supporters say is a Kafkaesque attempt to blacken his name beyond the grave.

"The people who persecuted Sergei when he was alive are the same people who continue to do that after his death, in order to cover up something they have done," said Ms Zharikova, who spoke from a secret location because of fears of retribution from the Russian authorities. "They obviously want to get a piece of paper stating that Sergei is guilty. The idea is to discredit the Magnitsky Act and any attempts to introduce similar laws in other countries."

Natalya Magnitskaya weeps over her son’s coffin

Russia's general prosecutor's office claims that the trial is going ahead at the request of the Magnitsky's family, because they expressed a wish to clear his name. Ms Zharikova however, a trained lawyer who met her husband when they were at high school, said it was "a lie" that she and his mother, Natalya Magnitskaya, wanted the prosecution.

"I have never asked for this trial," she said. "I don't want it and I told the investigators when I met them last summer that we, Sergei's relatives, didn't ask for it and we are against it. How can you try a dead person? A person has a fundamental right to defend himself in court. This is the law. You can't do that if you're dead. This is nonsense."

Critics say the Government's attempts to patch up relations with Russia and preserve strong business ties must not become appeasement of an increasingly autocratic Kremlin.

Richard Ottaway, chairman of the foreign affairs select committee, urged the Government in a Commons debate last week to name any individuals who were banned from entering the UK over Mr Magnitsky's death.

Bill Browder, the UK-based head of Hermitage Capital Management, the investment fund for which Mr Magnitsky worked in Moscow, said "The British government saying that it could ban human rights abusers is not enough. The point is that specific people should be named and shamed as a deterrent for others who want to do the same thing. The only acceptable response to this issue is to publicly ban the people who killed Sergei Magnitsky from coming to the UK."

Mr Browder compared the prosecution of his dead colleague to the Cadaver Synod, the posthumous trial of Pope Formosus, whose body was exhumed in 897 and propped in a chair in a Roman church to face charges of perjury. "It's that absurd, and that historic," he said.

Ms Zharikova, who has two sons, now aged 11 and 20, said the family had been devastated by her husband's persecution.

She was only allowed to visit her husband once in jail after he was arrested in November 2008, shortly before he died almost a year later.

Their children were refused permission to speak to him on the telephone.

She took regular food parcels of fruit, vegetables, tea, and chocolate to Mr Magnitsky in prison, but saw him getting thinner and paler at court appearances, where he pleaded to let be free, saying he was being maltreated and "held hostage" at the behest of the tax fraudsters he exposed.

"They created inhuman conditions for Sergei in prison," said Ms Zharikova. "His death is an irreplaceable loss. More than three years have passed since he died and every day the children and Sergei's mother and I recall moments with him, the time we spent together. They same time heals the pain but we haven't felt that."

She added: "Before Sergei's arrest, I had an almost total conviction that if a person is honest, has done nothing wrong and lives peacefully, then nothing [bad] will happen to him. Now that feeling has gone." The only comfort was hearing reports that some prison inmates had been spared persecution because the furore over her husband's death made guards more cautious. "So maybe Sergei didn't die completely in vain," said Ms Zharikova. "That's a ghostly consolation but it's something.